Print Email Facebook Twitter Benefits of curved serrations on broadband trailing-edge noise reduction Title Benefits of curved serrations on broadband trailing-edge noise reduction Author Avallone, F. (TU Delft Wind Energy) van der Velden, W.C.P. (TU Delft Aerodynamics) Ragni, D. (TU Delft Wind Energy) Date 2017 Abstract Far-field noise and flow field over a novel curved trailing-edge serration (named as iron-shaped serration) are investigated. Spectra of the far-field broadband noise, directivity plots and the flow-field over the iron-shaped serration are obtained from numerical computations performed using a compressible Lattice-Boltzmann solver. The new design is compared to a conventional trailing-edge serration with a triangular geometry. Both serration geometries were retrofitted to a NACA 0018 airfoil at zero degree angle of attack. The iron-shaped geometry is found to reduce far-field broadband noise of approximately 2 dB more than the conventional sawtooth serration for chord-based Strouhal numbers Stc<15. At higher frequencies, the far-field broadband noise for the two serration geometries has comparable intensity. Near-wall velocity distribution and surface pressure fluctuations show that their intensity and spectra are independent on the serration geometry, but a function of the streamwise location. It is found that the larger noise reduction achieved by the iron-shaped trailing-edge serration is due to the mitigation of the scattered noise at the root. This effect is obtained by mitigating the interaction between the two sides of the serration, by delaying toward the tip both the outward (i.e., the tendency of the flow to deviate from the centerline to the edge of the serration) and the downward (i.e., the tendency of the flow to merge between the upper and bottom side of the serration) flow motions present at the root of the sawtooth. Subject aeroacousticsnoise reductiontrailing-edge serrationturbulent boundary-layer trailing-edge noise To reference this document use: http://resolver.tudelft.nl/uuid:7ac97a0a-6419-4187-9c4e-bc5ef11753cc DOI https://doi.org/10.1016/j.jsv.2017.04.007 Embargo date 2019-04-22 ISSN 0022-460X Source Journal of Sound and Vibration, 400, 167-177 Part of collection Institutional Repository Document type journal article Rights © 2017 F. Avallone, W.C.P. van der Velden, D. Ragni Files PDF Beneficial_effect_of_curv ... _final.pdf 1.49 MB Close viewer /islandora/object/uuid:7ac97a0a-6419-4187-9c4e-bc5ef11753cc/datastream/OBJ/view